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Figure B-14 presents the sulfate concentrations for wells GC-3, P-1, P-3, J-1 and COY. The <br />sulfate concentrations in alluvial well P-1 declined in 2006 and 2007 after higher values over the <br />last few years at levels within historical natural values for this well. The Lewis Shale well P-3 was <br />dry during 2007. The 2007 sulfate concentration for Johnson Gulch well J-1 was similar to recent <br />higher values and slightly higher than the natural level in the Flume Gulch alluvium at well COY <br />but could be due to the previous dry cycle. Sulfate concentrations in the Flume Gulch wells (GC-3 <br />and COY) have fluctuated from approximately 300 to 1200 mg/1. <br />3.3 pH <br />Field pH is an important parameter to monitor because some coal spoils have the potential <br />to increase acidity of the ground waster, which increases the mobility of most heavy metals. A pH of <br />less than 5 would generally be needed to greatly increase the mobility of most heavy metals. <br />vailable H data is tabulated in Table B-1 of A ndix B. The field pH of water from the <br />A p Ply <br />GC wells has generally been slightly above 7.0 and has been ~at similar values since the initiation of <br />disturbance in this area. <br />Field pH from well GD-2 slightly decreased in 2005 and slightly above neutral the last two <br />years. The upgradient mining in the QR seams has not significantly affected the pH in this area of <br />the aquifer. The pH values from backfill well GD-3 are 6.8 and 6.6 for 2007, which is near the <br />values in the native aquifer at well GD-2. <br />Similar pH values were observed for the HI aquifer at well GF-4 in 2007 to those observed <br />in previous years. Backfill well GF-S had field pH values above 7.0 in 2007, while the field pH for <br />backfill well GF-7 was neaz neutral. The field pH values in backfill well GF-11 for 2007 were <br />C <br />Trapper Mining Company - 3-7 <br />2007 Annual Report <br />